1. Field of the Invention
The subject matter described herein relates generally to automated motion controllers and, more particularly, to jerk limited trajectory planning.
2. Related Art
Path planners or path generators typically comprise motion controllers. Path planners are used to control mechanical devices requiring motion and determine the movements of controlled elements in the mechanical devices. Mechanical devices that employ path planning can be found in various industrial systems such as manufacturing, assembling, packaging and other capacities. Servomotors, for example, are one such type of device. Other motors may control the movements of elements such as drill bits or robotic arms.
Path generators use various kinetic path algorithms along with discrete time controllers to provide path profiles. The path profiles are based on specified motion parameters. The specified motion parameters may include the following command inputs: end position, maximum velocity, maximum acceleration, maximum deceleration, and commanded jerk. The move's initial conditions are defined by the initial state of the path planner, so initial position, initial velocity, initial acceleration, and initial jerk are also known values.
Jerk is defined as the rate of change of acceleration or acceleration slope. Thus, jerk is the derivative of acceleration and is an important variable in many applications where a smooth start is required. The kinematic equations for generating constant jerk paths from an initial position to a final position subject to acceleration, deceleration, and velocity constraints are well known. Therefore, the known values stated above along with the kinematic equations form an equation set that can be then solved to yield the desired trajectory.
The interrelated kinematic equations can be solved prior to performing any motion based on the known/unknown variables. This method does result in a solution, but it requires complex calculations that are not readily adaptable to real time implementations. Furthermore, in many cases, a complex solution results that does not yield a closed form.
Therefore, a means to generate a time based profile that satisfies the initial and final conditions while not exceeding programmed limit values is desirable as well as providing a solution set that can be solved in a real time controller.